A motion control system is a means of controlling the position of at least one axis in an automated machine or plant. Example applications may be machine tools, robots, packaging machines, tape slitting machines, printing machines and pick-and-place machines.
It is known to communicate motion command values from a trajectory generator to one or more servo controllers by means of a serial network. Serial motion control networks have been implemented using either networks specifically designed for this purpose or using general purpose networks.
A practical consequence of using a serial network is that the motion control system acquires the characteristics of a sampled-data system.
Networked motion control systems have many advantages and have been widely adopted. However, they are not without some practical issues. For example, it would be desirable to eliminate or reduce rough motion that may be caused by infrequent updates of position and/or velocity command by computing intermediate, interpolated command values. It would be desirable for such an interpolation to be carried out using circuitry and/or techniques applicable to any number of axes and along any path of motion, yet using circuitry and/or techniques that do not rely on complex circuitry and/or complex numerical techniques, such as fitting polynomials. It would also be desirable to ease or eliminate synchronicity constraints dictated by a network update rate and the hierarchy of position, velocity and torque loops. It is also desirable to be able to reliably handle momentary interruptions in network communication, and safely perform motion-halting operations that may be needed in the event of system malfunctions, such as ramping down to a zero velocity. Accordingly, it is desirable to provide improvements to a networked motion control system.